Creep and shrinkage prediction models for concrete water retaining structures in South Africa

Mucambe, Edson Silva David (2010-12)

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010.


ENGLISH ABSTRACT: Concrete water retaining structures (WRS) in South Africa are under scrutiny due to the numerous durability problems that they have experienced lately; despite the efforts by local and national authorities in conserving these structures. At the heart of these problems are the creep and shrinkage phenomena. While shrinkage is the reduction of concrete volume with time, creep is defined as the time-dependent increase of concrete strain under constant or controlled stress. Both phenomena are affected by conditions to which WRS are exposed hence their accurate prediction is required. Numerical models have been developed to calculate the extent to which concrete creeps or shrinks over time. The objective of this thesis is to identify which of these models is better equipped to be used in South African WRS design. This is achieved through a systematic method that involves an investigation into the contents of these models and a statistical comparison of model calculations to WRS representative data. In partnership with reputable universities, a pioneer experimental creep and shrinkage data base is created in this project from which the WRS related data is selected. While investigating the contents of the numerical models, their applicability to South African WRS is identified and the integrity of model contents is assessed. Indeed, a few irregularities are found in the process and are presented in this thesis. The model calculations are statistically compared to data in the form of individual experiments as well as in the form of groups of experiments with similar concretes to find the ideal prediction model for different types of concretes as well. Also pioneered in this project is a weighted criteria and point system in which the findings of the model content assessment and statistical evaluations are incorporated. It is based on this system that conclusions are drawn and the most suitable prediction model for WRS design in South Africa is selected.

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